Electromagnetic interference shielding and radiation absorption in thin polypyrrole films

Results of permittivity measurements, electromagnetic interference shielding effectiveness, and heat generation due to microwave absorption in conducting polymer coated textiles are reported and discussed. The intrinsically conducting polymer, polypyrrole, doped with anthraquinone-2-sulfonic acid (AQSA) or para-toluene-2-sulfonic acid (pTSA) was applied on textile substrates and the resulting materials were investigated in the frequency range 1–18 GHz. The 0.54 mm thick conducting textile/polypyrrole composites absorbed up to 49.5% of the incident 30–35 W microwave radiation. A thermography station was used to monitor the temperature of these composites during the irradiation process, where absorption was confirmed via visible heat losses. Samples with lower conductivity showed larger temperature increases caused by microwave absorption compared to samples with higher conductivity. A sample with an average sheet resistivity of 150 Ω/sq. showed a maximum temperature increase of 5.27 °C, whilst a sample with a lower resistivity (105 Ω/sq.) rose by 3.85 °C.

Cracking and blowout in an aluminium high-pressure die casting die

Die cracking and metal blowout have been identified as problems in production of the structural sump, a high pressure die cast aluminium part, at Ford's Geelong manufacturing plant. Visual inspection, thermography and strain measurements have been performed and results are consistent with the view that cracking and blowout are caused by excessive stresses and deflections, respectively, generated by bending of the sliding cores. Models are being developed for finite element simulation of the stresses and deflections in the die during production, with a view to eliminating the aforementioned problems.

Industrial application of thermal image processing and thermal control

Industrial application of infrared thermography is virtually boundless as it can be used in any situations where there are temperature differences. This technology has particularly been widely used in automotive industry for process evaluation and system design. In this work, thermal image processing technique will be introduced to quantitatively calculate the heat stored in a warm/hot object and consequently, a thermal control system will be proposed to accurately and actively manage the thermal distribution within the object in accordance with the heat calculated from the thermal images.

Integrated optimization system for high pressure die casting processes

High pressure die casting (HPDC) is a versatile process for producing engineered metal parts by forcing molten metal under high pressure into reusable steel dies. However there are a large number of attributes involved which contribute to the complexity of the process. A novel integrated approach is developed to optimize the high pressure die casting processes. The die temperature profiles will be studied with infrared thermograph technology and the internal cooling system will be optimized to provide even cooling to the components and the die. The heat stored in the die and the components is studied with image processing. Based on the geometrical profile of the components, cooling channels can be redesigned to improve the cooling efficiency while the cooling time is reduced. This will not only significantly improve the quality of the castings but also improve the productivity of the process.

The influence of polymerization time and dopant concentration on the absorption of microwave radiation in conducting polypyrrole coated textiles

Temperature changes in conducting polypyrrole/para-toluene-2-sulphonic acid (PPy/pTSA) coated nylon textiles due to microwave absorption in the 8–9 GHz and 15–16 GHz frequency ranges were obtained by a thermography station during simultaneous irradiation of the samples. The temperature values are compared and related to the amounts of reflection, transmission and absorption obtained with a non-contact free space transmission technique, indicating a relationship between microwave absorption and temperature increase. Non-conductive samples showed no temperature increase upon irradiation irrespective of frequency range. The maximum temperature difference of around 4 °C in the conducting fabrics relative to ambient temperature was observed in samples having 48% absorption and 26.5 ± 4% reflection. Samples polymerized for 60 or 120 min with a dopant concentration of 0.018 mol/l or polymerized for 180 min with a dopant concentration of 0.009 mol/l yielded optimum absorption levels. As the surface resistivity decreased and the reflection levels increased, the temperature increase upon irradiation reduced.

Cooling effect of MWCNT-containing composite coatings on cotton fabrics

Multiwalled carbon nanotubes (MWCNTs) were dispersed in an aqueous solution of epichlohydrin based resin with the aid of a surfactant. The MWCNT-resin solutions were applied onto cotton fabrics to form a thin coating with different MWCNT contents (0, 11.1, 20.0, 33.3, and 50%). The thermal conductivity of the fabrics was measured based on the Newton’s law of cooling. The coating containing 50% MWCNTs showed 151% increase in the thermal conductivity. Infrared thermography was used to characterize the heating/cooling behavior of the fabrics. On contact with a 50°C hot surface, coated fabric that had 50% MWCNTs in the coating layer showed a 3.9°C lower equilibrium surface temperature than the untreated fabric. The cooling rate increased with increasing the MWCNT content within the coating layer. Such an effective cooling performance was attributed to the increased thermal conductivity and surface emissivity of the MWCNT-containing coating layer. The coating showed little influence on water contact angle of the coated fabrics, but slightly decreased the air permeability.

High thermal gradient in thermo-electrochemical cells by insertion of a poly(vinylidene fluoride) membrane

Thermo-Electrochemical cells (Thermocells/TECs) transform thermal energy into electricity by means of electrochemical potential disequilibrium between electrodes induced by a temperature gradient (ΔT). Heat conduction across the terminals of the cell is one of the primary reasons for device inefficiency. Herein, we embed Poly(Vinylidene Fluoride) (PVDF) membrane in thermocells to mitigate the heat transfer effects - we refer to these membrane-thermocells as MTECs. At a ΔT of 12 K, an improvement in the open circuit voltage (Voc) of the TEC from 1.3 mV to 2.8 mV is obtained by employment of the membrane. The PVDF membrane is employed at three different locations between the electrodes i.e. x = 2 mm, 5 mm, and 8 mm where 'x' defines the distance between the cathode and PVDF membrane. We found that the membrane position at x = 5 mm achieves the closest internal ΔT (i.e. 8.8 K) to the externally applied ΔT of 10 K and corresponding power density is 254 nWcm-2; 78% higher than the conventional TEC. Finally, a thermal resistivity model based on infrared thermography explains mass and heat transfer within the thermocells.